{Normally neither player would choose to pass if there were any worthwhile moves to be made on the board (even if they did not have to give up a pass stone). Thus, the exchange of a pass stone with the opponent also serves as a signal that the player passing believes that the game is over. Of course, the opponent is free to continue to play if he or she believes that there are worthwhile moves left to make, and the player who passed is free to respond.}
8) Illegal Moves:An illegal move is one violating the rules. If a player makes an illegal move-such as moving twice in a row (i.e., before the opponent has made a response), attempting to play on an occupied intersection, self-capture, or retaking a ko so as to repeat the full board position, the player must take back his or her move (both moves, if he or she moved twice in succession), it shall be treated as a pass, and a pass stone exchanged.
An illegal move must be noted as such by the opponent before he or she makes his or her move. When a player moves, he or she is tacitly accepting the opponent's previous move as valid. In particular, if it is discovered that an earlier move by one of the players was illegal, the game must nevertheless be continued as it stands unless both players agree to restore the earlier board position and proceed from that point.
9) Ending the Game:Two consecutive passes signal the end of the game. After two passes, the players must attempt to agree on the status of all groups of stones remaining on the board. Any stones which the players agree could not escape capture if the game continued, but which have not yet been captured and removed, are termed dead stones. If the players agree on the status of all such groups, they are removed from the board as prisoners of the player who could capture, and the game is scored as in Rule 12. If there is a disagreement over the status of some group or groups, play is resumed as specified in Rule 10.
10) Disputes:If the players disagree about the status of a group of stones left on the board after both have passed, play is resumed, with the opponent of the last player to pass having the move. The game is over when the players agree on the status of all groups on the board, or, failing such agreement, if both players pass twice in succession. In this case any stones remaining on the board are deemed alive. Any stone or group of stones surrounded and captured during this process is added to the capturing player's prisoners as usual.
{It is recommended, particularly if the players do not share a common language, that the following procedure be used to determine agreement on the status of groups. After two consecutive passes, the next player touches each connected string of opposing stones on the board which he or she believes to be dead. If the opponent disagrees, he or she also touches the same string. When a player is done indicating groups he or she believes are dead, he or she passes, passing a stone to the opponent as usual, and the opponent follows the same procedure. At any point, a player may resume play rather than continuing to indicate dead groups or passing. If both players pass and there was no disagreement indicated, the game is over, and all groups which the players have indicated as dead are removed from the board. If they both pass while a disagreement still exists, all stones remaining on the board are alive, and the board is counted as it stands. (The burden is thus effectively on the player who would be disadvantaged by such a result to resume play in the event of a disagreement.)
11) The Last Move:White must make the last move-if necessary, an additional pass, with a stone passed to the opponent as usual. The total number of stones played or passed by the two players during the entire game must be equal.
12) Counting:There are two methods for counting the score at the end of the game. One is based on territory, the other on area. The players should agree in advance of play which method they will use. If there is no agreement, territory counting shall be used.
(Although players' scores may differ under the two methods, the difference in their scores, and hence the game result, will be the same.)
Territory: Those empty points on the board which are entirely surrounded by live stones of a single color are considered the territory of the player of that color.
(At the end of the game, the empty points remaining on the board fall into regions. A region is the smallest set of empty points containing a given empty point and any empty points adjacent to any empty point in the set. That is, a region consists of those empty points which can be reached from a given empty point by moving only to adjacent empty points. A region is entirely surrounded by stones of a single color if the only stones adjacent to empty points in the region are of that color. There are situations (Japanese seki) in which a region of empty points is left at the end of the game which is not entirely surrounded by stones of a single color, and which neither player would fill because to do so would bring dire consequences. See Figure 4. When counting by territory, it is also possible that there will be some neutral points left between live groups belonging to the two players which have not been filled, although it is customary to fill all such points before scoring the game.)
Figure 4. Seki
Area: All live stones of a player's color left on the board together with any points of territory surrounded by a player constitute that player's area.
Neutral Points: Any empty points left on the board at the end of the game which are not completely surrounded by either player's stones are known as neutral points, and are not counted toward either player's territory or area. (There will rarely be any such points.)
Counting by Territory: When counting by territory, players add up their total territory less any prisoners held by the opponent (including dead stones removed at the end of the game). The player with the greater total (after adjusting for any compensation offered according to Rule 3) is the winner.
(It is customary for the players to fill in their opponent's territory with their prisoners, and to then rearrange their territories to facilitate counting. These are merely mechanical conventions to simplify counting.)
Counting by Area: When counting by area, the players add up their total area.Prisoners are ignored. The player with the greater total area (after adjusting for any compensation offered according to Rules 3 and 4) is the winner.
(In fact, since the total of the two players' areas will sum to 361, less any neutral points left on the board in seki, it is generally only necessary for one of the two players to count their area; if it exceeds 180, (or 180 adjusted for half of any neutral points in seki), they are the winner. It is customary for the player doing the counting according to this method to fill in his or her territory and then rearrange the stones into convenient heaps. Again, these are merely mechanical conventions to simplify the counting process.)
